Fuse and method of expelling fuse wire therefrom



July 11, 1933.

J. B. TRESCOTT 1,917,781

FUSE AND METHOD OF EXPELLING FUSE WIRE THEREFROM Filed Aug. 5, 1929 lA/VEINTOE k/ o/wv ,5. 77656025.

Patented July 11, 1933 UNITED STATES PATENT OFFICE JOHN' B. TRESCOTT, OF OVERLAND, MISSOURI, ASSIGNOR, BY MESNE ASSIGNMENTS, TO JAMES R. KEARNEY CORPORATION, OF ST. LOUIS, MISSOURI, A. CORPORATION OF MISSOURI FUSE AND METHOD OF EXPELLING FUSE WIRE THEREFROM Application filed August 5, 1929.

My invention relates to new and useful improvements in fuse wires which are used as a protective measure in various electric circuits in connection with various types of fuse holders, fuse tubes, and fuse wire holding devices, to improvements in the method of limiting the time of arcing upon rupture of the fuse wire.

More particularly it relates to an explosive type of fuse for high tension lines in which a. small explosive charge is utilized to expedite the rupture of the fuse at times of over load, and when the fuse is mounted in a partially closed tube the explosive acts to expel the burnt-out fuse wire and other products of combustion and also assist in preventing the electric are from maintaining itself across the gap caused by the blowing, burning, or melting of the fuse wire.

A conventional type of high tension fuse consists of a pair of spaced terminals, between which a fuse wire of suitable material and resistance is connected. The two terminals are oined by a fiber tube which serves to enclose the fuse wire. The upper terminal is customarily closed in while the lower terminal is open at the bottom in the manner illustrated in Figure l of the present drawing. WVhen the load on the circuit becomes greater than the capacity of the fuse wire, this wire melts and establishes a gap which is intended to break the circuit. If the overload is very heavy or a dead short circuit, the melting or fusion of the fuse wire is so rapid as to be the equivalent of a mild explosion. However, if the overload is slight, barely enough to cause fusion as is usually the case, there is a minute break in the fuse wire across which an arc is formed. This small gap does not disconnect the circuit so long as the arc is maintained between the severed ends of the fuse wire. The overload which is continued holds the fuse wire at approximately a melting temperature and the additional heat of the arc supplies the neces sary surplus heat to melt the wire and slowly widen the gap. The fusion or melting of the fuse wire generates a metallic vapor which fills the fuse chamber with a gas of high electric conductive properties. This gas Serial No. 383,735.

materially aids in establishing and sustaining an are. When the fuse wire rupture is of the more common slow melting kind, the gradual widening of the gap draws out the arc to a much greater length than it would ordinarily be able to jump. The are not only serves to keep the circuit closed after it should have been broken, but it also destroys the fibrous tube in which the fuse wire is enclosed and otherwise damages the fuse fixture.

The use of a protective tube to enclose the fuse wire prevents any appreciable circulation of air which would displace the vapor generated by its fusion so the overloaded circuit is maintained by jumping a gap of greater width than its normal limit. As the arcing continues to melt the fuse wire, more vapor is generated and cases have been noted where the entire fuse wire has been consumed and arcing established between the fuse terminals which was continued until the fiber-protective tubing was burned through.

It is not uncommon in high tension lines to find the entire fuse irreparably damaged by being burned in this manner. This requires a comparatively expensive replacement where ordinarily the fuse wire alone should be replaced.

With the foregoing in mind, my principal object is to provide a high tension fuse wire with means to limit the time of arcing upon its rupture.

Another object is to provide means for expelling the unmclted parts of the fuse wire assembly and gases from consumed parts from the fuse tube upon burning of the fuse.

A further object is to fill the tube with a vapor of combined high dielectric and fire extinguishing properties.

A still further object is to prevent injury to the fuse terminals and tubing upon burn ing of the fuse.

An additional object is to permit the use of a shorter length fuse than is customarily used without diminishing the factor of safety against arcin With the foregoing and other objects in view, my invention consists in certain novel features of construction and arrangement of parts, hereinafter more fully described and claimed, and illustrated in the accompany ing drawing in which Figure 1 is a cross section taken through a high tension fuse assembly.

Figure 2 is an enlarged longitudinal sectional view showing the fuse cartridge indetail.

Figures 3, t, and 5 are longitudinal sections similar to Figure 2 showing different arrangements of the cartridges.

The numeral 1 in the drawing indicates the lower terminal or base of a high tension fuse assembly having a cylindrical opening passing longitudinally therethrough. 2 is the upper terminal into which extends a longitudinal cylindrical opening that terminates within the terminal. The lower or outer portion of this opening is preferably somewhat larger than the inner portion and is threaded at 3 to receive and engage the inner fiber tube 4. The inner tube 4 projects through the opening of the base 1. and is engaged by a set screw or other suitable means, not shown. An outer tube 5 is usually placed over inner tube 4 between the two terminals. The upper end of inner tube i is threaded and adapted to engage the threads 3 of terminal 2. The inner portion 6 of the opening in the upper terminal 2 is of the same diameter as the inside of tubing 4 so that when the tube is screwed to its limit, the inside of the fuse assembly is smooth and continuous.

Fuse wire 7 is preferably a single wire having a disk-like end 8. Disk 8 is adapted to rest on surface 9 within the opeping'in upper terminal 2 and stud 10 passing through the side of this terminal engages the disk and holds it in place. The lower end of the fuse wire passes through the opening in the base and is connected on a stud threaded into the outer side of this member. Fixed on fuse wire 7 adjacent to disk 8 is a capsule 11 of substantially less diameter than the inside of tube t and the portion 6 of the opening in the upper terminal 2. This capsule is preferably formed of celluloid or some similar combustible material.

Fuse wire 7 is nicked at 12 within the capsule so that it will be blown out at this point. Capsule 11 contains a small charge of nitro powder 13 and a volatile iire extinguishing powder 14 of high dielectric properties. These powders are separated from each other. lVhile any efficient fire extinguishing powder may be used, a powder formed of the following properties has been found desirable.

Sodium chloride i parts Sodium bicarbonate 3 parts Sodium sulphate 1 part Calcium chloride; 1 part Sodium silicate 1 part The preferred form of capsule is that shown in Figure 2 wherein the capsule comprises a celluloid cylinder 15 which is seated against disks 16 at either end. Disks 16 are preferably forn'ied of fibrous material but they may be metallic without affecting the proper operation of the fuse. The main body of cylinder 15 is filled with fire extinguishing powder 14. Explosive powder 1?, is spaced from the fuse wire 7 and located in the extreme upper and outer portions of cylinder 15. Spacing the explosive 13 from the fuse wire 7 tends to slightly delay the ignition since the heat must pass through the fire extinguishing powder 14 which has relatively low conductivity. This spacing also provides a protective feature in that heating of the fuse after temporary overload which does not cause an actual rupture will not ignite the powder.

Upon ignition of the explosive powder 13 in cylinder 15 the disk 16 together with the unconsumed portions of fuse wire 7 are blown through tube l and out the open end in the lower terminal. The volatile fire extinguish ing powder 14 temporarily fills the tube but the force of the explosion carries out practically all the gases, leaving a partial vacuum which is immediately replaced by ordinary atmosphere. Thus any metallic vapor which may have been generated is removed and the circuit is immediately and effectually broken. A constant blow-out condition is established regardless of the manner of the overload, that is, whether it is slight or caused by a dead short circuit.

Figure 3 illustrates a slightly different form arrangement of the capsule. In this form small buttons 17 grip the fuse wire 7 at either end of the capsule 18. Explosive powder 13 occupies a central portion of capsule 18 throughout its cross sectional area and lire extinguishing powder 14 fills either end. The nicked rupture point 12 of the wire is located within the lower section of fire extinguishing powder. In this type capsule, the expansive force of the explosive powder is relied upon to expel the fuse wire from the upper end of the tube 4. The lower section of tire extinguishing powder breaks the arc as it passes out and the upper section of this material is provided as a precautionary measure.

(lapsule 19 shown in Fi gu re 4 grips the fuse wire and holds its position without the aid of other parts. The powder arrangement is such that there is a complete mixture of the fire extinguisher and explosive after igni tion but the original arrangement is such that the fire extinguisher 14 separates the explosive 13 from contact with the fuse wire. In this style, the explosive occupies the peripheral portion of the cylinder throughout its length.

In. Figure 5 the fire extinguisher powder 14: and explosive powder 13 are in separate receptacles 20 and 21, respectively. Disks hold these receptacles in proper position, the lower disks also serving to expel the fuse wire upon igmtlon of the explosive.

5 The possibility of arcing governs the length of the fuse units for circuits of various voltages. It can be readily seen that a shorter fuse of my type can be used for the same work in place of the lengths now required. The use of a shorter fuse means that a smaller fuse bracket can be used which effects a substantial initial economy. A further advan tage is that innumerable fuses may be blown out in a fuse unit without causing damage, the only replacement required being the fuse wire and powder capsule, whereas formerly it was quite common to have to install a cOmplete fuse unit.

It is to be understood that minor changes in the size, form, and construction of the various parts of my improved device can be made and substituted for those herein shown and described, without departing from the spirit of my invention as expressed in the following claims.

I claim:

1. A fuse having a fixed rupture point enclosed by a Volatile substance of high dielectric properties, and a substance adapted to volatilize said dielectric substance.

2. A fuse having a fixed rupture point enclosed by a-volatile substance of high dielectric properties and relatively low thermal conductivity, and an explosive powder for volatilizing said dielectric substance.

3. In combination with a fuse cartridge having a pair of spaced terminals, a fuse wire connecting said terminals, and hav ng a fixed rupture point, an explosive material carried by said fuse wire in spaced relatlon to said -rupture point, said explosive bemg adapted to be ignited upon blowing of said fuse and to expel said fuse wire from said cartridge.

4. In combination with a fuse cartridge having a pair of spaced terminals, a fuse, having a predetermined point of rupture, and connecting said terminals, a volatile dielectric substance positioned adjacent said rupture point, and an explosive powder separated from said rupture point by said volatile substance.

5. In a fuse, the combination with spaced terminals, each having an axial bore, a fuse wire connecting said terminals, and a tube enclosing said fuse wire between said termi nals, of means including an explosive powder capsule carried by the fuse wire, for expelling said fuse wire from said tube through the bore of one of said terminals, upon rup ture of the fuse wire, the fuse wire being preformed to confine its zone of rupture to said capsule. 6. In a fuse, the combination with a terminal having an axial bore therethrough, a second terminal spaced from said first-mentioned terminal and having an axial bore terminating therein, a fuse wire connecting said terminals, and a tube enclosing said fuse wire between said terminals, of an explosive charge and a container therefor carried by the fuse wire within said second-mentioned terminal and adapted to be ignited upon rupture of said fuse wire to expel portions of said fuse wire from said tube through the bore of said first-nientionml terminal.

7. In a fuse, the combination with a terminal having an axial bore therethrough, a second terminal spaced from said first-mentioned terminal and having an axial bore terminating therein, a fuse wire having a fixed rupture point connecting said terminals, and a tube enclosing said fuse wire between said terminals, of an explosive charge carried by said fuse wire and spaced from said rupture point, said explosive being adapted to be ignited upon rupture of said fuse wire and blow portions of said fuse wire through said tube and out through the open bore of said first-mentioned terminal.

8. As a new article of manufacture, a fuse having a defined rupture point enclosed by a fluid-forming fire extinguishing powder, and an explosive substance spaced from said rupture point.

9. In a fuse link, a hollow body carried by, and between the ends of the link, a conducting portion of the link disposed within the body and serving to provide a defined location of rupture in said body, an arc quenching material and an explosive material within said body, said materials and location of rupture being arranged to delay ignition of said explosive material.

10. A fuse link including a celluloid container carried entirely thereby, a fluid-forming, fire-preventing material and an explosive material in said container.

11. A fuse link including a hollow body carried by said link, a solid,-fluid-forming extinguishing material and. an explosive material in said body, a readily fusible conducting portion of the link in said body, said extinguishing material being disposed between said explosive material and readily fusible link portion.

12. In combination, a fuse wire, a con tainer about the fuse wire, said wire extending from opposite ends of the container for purposes of connection, the fuse wire being formed to confine its rupture portion to a definite zone within the container, a gas forming extinguishing material and an. explosive material, said materials being disposed within said container and differently spaced from said rupture zone.

13. its a new article of manufacture, a fuse wire adapted for use with fuse cartridges of standard type, a capsule carried by the fuse wire, a defined rupture portion formed on the fuse wire within said capsule, a solid, gast'orming extinguishing material Within the capsule adjacent said point of rupture and an explosive material within the capsule and spaced from said point of rupture.

14. As a. new article of manufacture, a fuse wire adapted for use in an expulsion fuse cartridge, a container portion of readily franible. material carried by the wire and extending over a restricted portion of its length, there being a preformed rupture portion of the wire in said container, and pow dered materials within the container, one of such materials being adjacent said point of rupture, and another material spaced therefrom.

15. As anew article of manufacture, a fuse link having a fixed zone or" rupture, a container of a. readily destructible and inflammable substance carried by a portion of said link, an explosive material and an arc snuff ing material in said container, the explosive material being spaced from said zone of rupture.

16. As an article of manufacture, a fuse link having a readily combustible container supported upon and surrounding a portion, thereof and an arc snufiing substance, within said container.

17. In an electric fuse switch, the combination of an expulsion fuse tube with an explosive fuse link construction, said fuse link con struction comprising a fuse link, a portion of which is surrounded by a frangible capsule, said capsule containing an explosive substance adapted to explode the capsule when the link is heated to a predetermined temperature.

In testimony whereof I hereunto afiix my signature this 27 day of June, 1926.

JOHN B. TRESCOTT. 

